Effects of Human Leukocyte Dialysates Containing Transfer Factor in the Direct Leukocyte Migration Inhibition (LMI) Assay

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Abstract
We report on an evaluation of the direct leukocyte migration inhibition (LMI) test as a potential in vitro assay of Transfer Factor activity. Crude dialysates of human leukocyte extracts containing Transfer Factor (DLE) were observed to cause both antigen-dependent and antigen-independent effects on the migration of nonimmune leukocyte populations. We find that only those DLE preparations that are obtained from donors with intense cutaneous DTH reactions to antigen have the capacity to cause antigen-specific effects consistently, and DLE obtained from donors with moderate or absent cutaneous reactivity are generally not active in this regard. Additionally, this antigen-specific activity of DLE is dose dependent. These two variables are consonant with similar requirements for successful in vivo transfer of cutaneous DTH. The pulsing of nonimmune migrating cell populations with immune DLE for 30 to 60 min is an additional requirement for maximum effects to be achieved. When these experimental conditions are met, there is a strong suggestion that antigen-specific inhibition of migration can be conferred by DLE on nonimmune cell populations, which is concordant with the pattern of cutaneous DTH reactions expressed by the donor of DLE. The data suggest further that the component(s) of DLE responsible for this activity resides in a >3500 m.w. dialysis fraction and it does not behave like a superantigen or a chemotactant in this assay system. When immune DLE is incubated with immune leukocyte populations, the anticipated inhibition of migration in the presence of antigen is not augmented but is abrogated instead. The antigen specificity of such suppressor-like activity is currently under investigation. We conclude that the LMI test appears to provide a suitable in vitro assay to investigate further the nature and mechanism of action of DLE and its components and provide a means of separating the moiety or moieties responsible for antigen-specific effects before in vivo testing.